Now I have managed 8 trainings with short (about 1Mile) BF-sections (minimalshoes in my hands, great advice Michael!). I'm very happy that after some really painful days my feet are getting more resistant. The part on asphalt is no problem, but I aim to achieve running on forest tracks.
Today I was able to run some minutes on a track covered with very small broken stones without "ouch!" But the tracks that are very soft natural duff with numerous pebbles are so brutal!! The stones seem to penetrate deeply into the tissue.
I wonder if one day I'll be able to run this tracks with a smile on my face? I keep at it!